TUESDAY, July 17 (HealthDay News) -- For the second time in less than a month, U.S. drug regulators on Tuesday approved a new weight-loss medication.

Qsymia -- formerly dubbed Qnexa -- is a combination of the drugs phentermine and topiramate, and is manufactured by the pharmaceutical firm Vivus Inc.

"Obesity threatens the overall well being of patients and is a major public health concern," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in an agency news release issued late Tuesday. "Qsymia, used responsibly in combination with a healthy lifestyle that includes a reduced-calorie diet and exercise, provides another treatment option for chronic weight management in Americans who are obese or are overweight and have at least one weight-related comorbid condition."

The drug is approved only for the obese (people with a body-mass index, or BMI, of 30 or above) or overweight people (body mass 27 or higher) who also suffer from conditions such as hypertension, type 2 diabetes or high cholesterol. It will be available in a standard dose but also a higher dose "for select patients," the FDA said.

Last year, a study funded by Vivus found that obese patients taking Qsymia lost an average of 22 pounds over a year, while also lowering their blood pressure and cholesterol levels.

On June 27, the FDA gave its OK to another weight-loss drug, Belviq (lorcaserin), which was approved for obese adults who have high blood pressure, high cholesterol or type 2 diabetes, and is to be used in combination with a low-calorie diet and exercise.

The back-to-back approvals followed a 13-year stretch in which the FDA did not approve any new medications to help people struggling with overweight or obesity to lose unwanted and unneeded pounds.

In May, a study presented at the European Congress on Obesity in Lyon, France, found that volunteers who took Qsymia experienced substantial weight loss, even if they had many weight-related health problems. The 56-week clinical trial included 994 patients who took a placebo, 498 who took a medium dose of Qsymia, and 995 who took a high dose of the drug.

Back in February, an FDA advisory panel recommended that the agency approve Qsymia for the treatment of obesity. The advisers concluded that Vivus, based in Mountain View, Calif., had supplied enough clinical data about the drug's benefits and risks.

While effective at reducing weight, Qsymia was initially denied FDA approval in 2010 because of potential side effects, including heart palpitations and birth defects -- such as cleft lip in babies -- if taken by pregnant women.

In fact, the FDA is stressing that "Qsymia must not be used during pregnancy because it can cause harm to a fetus." The drug is also not recommended for people with either glaucoma or hyperthyroidism, and because it can boost the heart rate it should not be taken by people who have had a stroke or unstable heart disease within the past six months, the FDA said.

Qsymia also comes with a special Risk Evaluation and Mitigation Strategy (REMS), which includes an education guide for patients and providers. The drug can only be sold and dispensed by specially certified drug stores, the FDA added.

Before making its decision in February, the FDA advisers reviewed two years of data on the drug; when advisers previously voted on Qsymia, only one year's worth of follow-up data was available.

Qsymia combines the appetite suppressant phentermine (Adipex-P) and the anti-seizure/migraine medication topiramate (Topamax). Phentermine once was prescribed widely as the "phen" part of the fen-phen weight-loss drug, which was withdrawn from the market in 1997 after its use was linked to both high blood pressure in the lungs and heart valve disease. The problems were related to the "fen," or fenfluramine, part of the combination, not the phentermine, scientists said.

Belviq was also initially denied FDA approval. Manufactured by Arena Pharmaceuticals of Switzerland, the drug maker first sought approval in 2010 but was turned down because animal studies showed the drug was associated with tumor growth.

New data supplied to the FDA that allayed these fears led to the drug's approval last month.

Doctors and other health professionals agree that the best way to keep off unwanted weight is through a healthy lifestyle that includes proper nutrition and exercise. Still, the new drugs should benefit some of the estimated two-thirds of Americans who are either overweight or obese, experts said.

Samantha Heller, an exercise physiologist and clinical nutrition coordinator at the Center for Cancer Care at Griffin Hospital in Derby, Conn., told HealthDay that "obesity is often associated with alterations in endocrine function, metabolism, hormones that regulate appetite and more."

For many people struggling with weight, these disruptions in the balance of hormones and metabolism make it difficult to lose weight, she said. People may feel hungry all the time, fatigued or lethargic. Losing weight for people who are obese is rarely as simple as eating less, she added.

"People need to understand that lifestyle modifications are essential for successful weight loss, weight maintenance and fitness programs. The weight loss reported in the studies is modest and the placebo group lost weight too, indicating that ongoing lifestyle counseling and support have a positive impact with and without medication," she said.